The present invention relates to a photocurable resin composition, and particularly to a photocurable resin composition which is capable of photocuring even if it contains a white pigment such as titanium white. The present invention also relates to a method of producing a decorative material with excellent whiteness which has a light colored coating based on a pure-white color to a white color formed on a substrate, particularly a non-white inorganic substrate composed of cement, by using the photocurable resin. The present invention further relates to a method of producing a decorative material with excellent whiteness and hiding power which has a desired pattern or color tone transferred from a printed film to the above-described white decorative material, and particularly a decorative material which is useful for applications to building materials and decorative members.
When a coating material containing a large amount, for example, 10% or more, of white pigment such as titanium white is used in a photocuring system, the ultraviolet absorption range of the titanium white overlaps the range of wavelengths in which a initiator used for photocuring is decomposed and thus the photocuring is significantly inhibited. In order to prevent this inhibition, a photocuring system using a thioxanthone-based initiator and a amine sensitizer in combination is brought into practical use.
This system is effective, however, when the concentration of titanium white is not so high, but regretably has a problem in that, when a sensitizer is used in an amount that can effect curing, the system is yellowed, and thus a pure white coating cannot be obtained.
BASF AG. of West Germany has recently reported that the use of acylophosphine oxide enables photocuring even if titanium white is mixed in (refer to, for example, Japanese Patent Publication No. 8047.1985 and Japanese Patent Laid-Open No. 15471/1980). This sort of initiator produces improvements whereby the whiteness and the curing property of a coating in which titanium white is mixed are more excellent than with conventional initiators.
However, it is also apparent that, if titanium white is mixed in a high concentration, for example, 20% or more, curing is significantly inhibited, and a sufficient curing property cannot be obtained.
A method is also known in which a surface of a substrate, particularly an inorganic substrate composed of cement, is coated with a photocuring resin which is then subjected to photocuring so that the surface properties are improved. However, when a large amount (for example, 10% or more) of white pigment such as titanium white is used in a photocuring system for the purpose of obtaining a non-white base with a light color coating based on a pure white to white color, photocuring is significantly inhibited because the ultraviolet absorption range of the titanium white overlaps the wavelength range in which a photocuring initiator is decomposed.
In addition, a method is known in which a surface of a substrate such as a plastic product or an inorganic base is coated with a curable resin, and the printed surface of a film on which a desired pattern or a color tone is printed is made to adhere to the surface before the resin is cured, and then the curable resin is cured so that the pattern or color tone is transferred to the surfaces of the curable resin. However, when a non-white substrate is used, the tone of the substrate affects the pattern or color tone transferred, and thus a desired pattern or color tone often cannot be obtained. In such a case, the surface of the non-white substrate is generally coated with a white resin, and then subjected to transfer of the pattern or color tone to obtain a product with a pattern or color tone which exhibits excellent hiding power.
Recent improvements in a photocuring technique enable the use of a photocurable resin in the transfer of a pattern or tone so that the curing speed is increased. However, if a non-white substrate is coated with a photocurable resin in which a large amount (for example, 10% or more) of white pigment such as titanium white is mixed and then subjected to transfer, the photo-setting is remarkably hindered because the ultraviolet absorption range of the titanium white overlaps the wavelength range in which a photo initiator is decomposed, and thus a good product cannot be obtained.